As the Internet has evolved, the number of network-layer protocol addresses (2^32) has proved to be insufficient for maintaining full connectivity between the continually growing number of network devices attached to the Internet. For this reason, a new network-layer protocol, known as Internet Protocol version 6 (IPv6), has been designed to replace the currently deployed network-layer protocol, known as Internet Protocol version 4 (IPv4). The numbers 6 and 4 refer to the version numbers of the two protocols, respectively. This new address space, IPv6, supports 2^128 (which is approximately 3.4×10^38) addresses; thereby making astronomically more unique network-layer addresses available for Internet devices. See, e.g., Internet Engineering Task Force (IETF) Request for Comments (RFC) 2373 and RFC 2460.